On Fri, 18 Oct 2002, Joachim Worringen wrote:
> Donald Becker:
> > In the Scyld Beowulf system (well, specifically the professional
> > editions) we ship six different kernel variously optimized for
> > Pentium-4, Athlon, and uniprocessor/SMP. And with the current system
>> Can you elaborate on the actual performance differences/gains that these
> kernels show?
A uniprocessor kernel can show a substantial performance improvement
over SMP for many file system and network operations. This is
unimportant for compute-intensive applications which spend little time
doing system calls or I/O, but is measurable for systems which do
directory operations on large directories, pass many small messages, or
make heavy use of the page table entries.
> The things that I would optimize are memcpy() and maybe libm -
> but do you really need different kernels for this?
You are thinking about the user code. We don't switch libraries, we
switch the kernels. Check out the compile options and kernel code
changes (primarily page-table/memory-management and MMX copies) when the
various processor family optimizations are selected for the kernel.
--
Donald Becker becker at scyld.com
Scyld Computing Corporation http://www.scyld.com
410 Severn Ave. Suite 210 Scyld Beowulf cluster system
Annapolis MD 21403 410-990-9993